Fault Seals in Oil Fields in Nevada

Norman H. Foster, Harry K. Veal, Louis C. Bortz

Faults form seals for oil accumulations in the Eagle Springs, Trap Spring, and Blackburn fields, and probably in the Grant Canyon field, in Nevada. The main boundary fault on the east side of the Pine Valley graben forms a seal in the Blackburn field. A fault on the west side of the Trap Spring field forms a seal. In Grant Canyon field, it is interpreted that the main boundary fault on the east side of the Railroad Valley graben forms a seal.

Calcite is deposited by hot spring activity, plugging up many fault zones and, in some cases, forming seals. Some fault zones have calcite mineralization up to several thousand feet wide. Within the Eagle Springs field on the east side of the Railroad Valley graben, a northeast-trending fault separates oil accumulations with different oil-water contacts. This separation indicates that the fault forms at least a partial seal within the accumulation.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.